Method for extending the life of thin walled tubing and austempered weld stress relieved thin walled tubing

ABSTRACT

The present invention is directed to a method of extending the life of thin walled tubing by austempering the tubing in a controlled continuous run process involving heating, quenching, and cooling the tubing pursuant to predetermined process parameters. The invention is also directed to a process for austempering tubing having a welded seam and for relieving residual stress in the weld. The invention is further directed to the product of the above processes as well as an austermpered weld stress relieved thin walled tubing and such tubing in combination with other apparatus with which it is suitable for use in the production of hydrocarbons.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a method of extending the life of thin walled tubing by austempering the tubing in a controlled process involving heating, quenching, and cooling the tubing pursuant to predetermined process parameters. The invention is also directed to a process for austempering tubing having a welded seam and for relieving residual stress in the weld. The invention is further directed to the product of the above processes as well as an austempered weld stress relieved thin walled tubing and such tubing in combination with other apparatus with which it is suitable for use in the production of hydrocarbons.

2. Description of the Prior Art

Each instance tubing is rolled on or off a coil tubing reel, it is permanently elongated. The elongation accumulates until exhausted and the tubing breaks. Hence, elongation is a significant property of the tubing material.

The second significant property of tubing material is strength or hardness. This quality resists dialation stesses of pressure and tension stresses of deployments in deep wells.

A characteristic of steel is decreasing elongation with increasing hardness. Metallurgically, an ideal coil tubing is a paradox: hard for strength in deep or high pressure wells, ductile for repetitive reeling.

Present technology coil tubing steels have a martensitic structure. Martensite has unfavorable hardness versus elongation trade-off. On the other hand, austempered steels have a bainitic structure. Bainitic structured steels are not only hard, but also retain commendable elongation.

Austempering of steel is known in the prior art, however it is typically accomplished in a non-continuous batch process which is unsuitable for coil tubing milling.

Represented by FIG. 1 is the current technology to continuously mill steel tubing: metal strip is introduced to a tube formation device, the seam welded and scarfed, and the formed tubular annealed, e.g., by heating. The tubing is chilled by cooling apparatus, and then travels through additional formation devices, e.g., sizing rolls. The tubular may then be heated and cooled again and taken up, e.g., on a reel. By welding the butts of the strip stock at the front end of the process, very long lengths of tubing can be milled.

In the continuous tube milling process, the sizing operation in FIG. 1 work-hardens the tubing increasing the strength. The thermal processes depicted in FIG. 1 are either palliatives for problems caused by welding, or to soften tubing to the desired grade after work-hardening. The thermal processes used in present tubing milling technology do not harden the tube.

SUMMARY OF THE INVENTION

The present inventions are directed toward an apparatus and methods useful for increasing the strength of the tubing while maintaining the elongation of thin walled tubing by austempering the thin walled tubing. The present invention is further directed toward a method for austempering thin walled tubing comprising a welded seam and for stress relieving the welded seam. The present invention is also directed toward a product produced by the methods and/or processes described above. The present invention is also directed toward a thin walled austempered tubing comprising a stress relieved welded seam.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic overview of a prior art system.

FIGS. 2 and 2 a are schematic overviews of an exemplary apparatus for practicing the present inventions' methods.

FIG. 3 is a view in partial perspective of a section of austempered tubing.

FIG. 3 is a schematic view of an exemplary deployment of austempered tubing in a well.

FIG. 5 is a block diagram of a first method of the present invention.

FIG. 6 is a block diagram of a second method of the present invention.

FIG. 7 is a block diagram of a third method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 2, exemplary apparatus 10 for austempering thin walled tubing according to the methods of the present inventions comprises heater 20, low temperature reservoir 30, and cooler 40. Apparatus 10 is adapted to be used with continuous runs of tubing 12 while practicing the methods of the present invention. As used herein, a continuous run is one which processes a length of around 200 feet or more in a single processing procedure.

Metallic tubing 12 has a wall thickness of less than 0.25 inches, preferably around 0.120 inches. In an embodiment, metallic tubing 12 comprises a steel alloy with a carbon content greater than or equal to 0.25 and less than or equal to 0.45 and may comprise 4130 alloy steel. Metallic tubing 12 may be supplied from source 15 of a substantially continuous supply of metal, e.g. a rolled strip, and formed in to a tubular at tube former 90. Seams created by tube formation may be welded at seam welder 91 and the formed seam scarfed at scarfer 92.

Heater 20 is adapted to accept a section of metallic tubing 12 and heat the section to a high temperature in the range of 1300-1600° F. Heater 20 may comprise an induction heater and/or a flame or the like, or a combination thereof. Heater 20, e.g. an induction heater, may be located proximate to or within low temperature reservoir 30.

Low temperature reservoir 30 is adapted to accept a moving section of metallic tubing 12 as part of a continuous run process and to reduce the temperature of the section of metallic tubing to a first low temperature in the range of 500-1000° F. in a time period of less than 3 seconds. Low temperature reservoir 30 as used for quenching may comprise a molten salt bath. Moving may be accomplished by numerous equivalent means including by using rollers.

Cooler 40 is adapted to cool a section of metallic tubing 12 to a second low temperature below 100° F. Cooling may be accomplished by numerous equivalent means including by forced convection. Additional coolers may be present, e.g. water cooler 93, as is practiced in the art.

Additional processing may occur after the second cooling. For example, austempered metallic tubing 12 may be sized at sizing rollers 94 and cooled further by coolers 96 and 97.

Austempered metallic tubing 12 may then be taken up, e.g. at takeup reel 17.

Austempered thin walled welded tube 12 may be coiled on a reel, e.g., takeup reel 17, which may be further mounted on ship 16 (FIG. 2 a).

Referring to FIG. 3, austempered thin walled welded tube 12 may comprise first end region 12 a adapted to be attached to device 19, e.g. a motor, an overshoot jar, an intensifier, a landing nipple, a plug catcher, a casing scraper, a snake pin, a downhole tool, a valve, or the like. Austempered thin walled welded tube 12 may further comprise second end region 12 b opposite first end region 12 a which may be adapted to be further connected to device 18, e.g. a pump.

Austempered, thin walled, and stress relieved welded tubing 12 may be produced by any of the exemplary methods described herein. Moreover, thin walled welded tube 12 produced by any of the exemplary methods described herein may comprise an austempered cylindrical body created as part of the continuous run processes of those methods where the austempered cylindrical body comprises first seam edge 12 c, second seam edge 12 d, and a wall having a thickness of less than 0.25 inches. Thin walled welded tube 12 may further comprise stress relieved welded seam 12 e joining the first and second seam edges.

Referring now to FIG. 4, in an exemplary embodiment thin walled welded tube 12 is unspooled from takeup reel 17. One end of thin walled welded tube 12 is connected to pump 18 and the other end deployed through well casing 90 and/or production tubing 91, terminating in tool 19.

In the operation of exemplary embodiments, referring now to FIG. 5, in a first exemplary method for austempering thin walled tubing, a section of metallic tubing 12 (FIG. 2 a) is heated to a high temperature in the range of 1300-1600° F. in heater 20 (FIG. 2 a). The section of metallic tubing 12 has a wall thickness of less than 0.25 inches, preferably around 0.120 inches.

After being heated, the section of heated metallic tubing 12 (FIG. 2 a) is moved from heater 20 (FIG. 2 a) to low temperature reservoir 30 (FIG. 2 a) as part of a continuous run process. While in low temperature reservoir 30, the section of metallic tubing 12 is quenched to reduce the temperature of the section of metallic tubing 12 to a first low temperature in the range of 500-1000° F. in a time period of less than 3 seconds. Processing the section of metallic tubing 12 may comprise a time-temperature-transformation curve where the start of conversion to austentite-ferrite is at least 0.75 seconds after quenching in low temperature reservoir 30.

The section of metallic tubing 12 (FIG. 2 a) is allowed to transform to bainite and then moved out of low temperature reservoir 30 (FIG. 2 a) as part of the continuous run process and cooled to a second low temperature below around 100° F. Cooling may be by forced convection, e.g. at cooler 40 (FIG. 2 a).

In a second exemplary method, referring to FIG. 6, a further exemplary method for austempering thin walled coiled tubing 12 (FIG. 2 a) comprises extending a section of thin walled metallic tubing 12 having a wall thickness of less than 0.25 inches from a coil mounted about reel 15 (FIG. 2 a) into heater 20 (FIG. 2 a) as part of a continuous run process. The section of metallic tubing 12 is heated to a high temperature in the range of 1300-1600° F. in heater 20 and then moved from heater 20 to low temperature reservoir 30 (FIG. 2 a) as part of the continuous run process. In low temperature reservoir 30, the section of metallic tubing 12 is quenched in low temperature reservoir 30 to reduce the temperature of the section of metallic tubing 12 to a first low temperature in the range of 500-1000° F. in a time period of less than around 3 seconds.

The section of metallic tubing 12 (FIG. 2 a) is allowed to transform to bainite and then the section of metallic tubing 12 transformed into bainite is moved out of low temperature reservoir 30 (FIG. 2 a) as part of the continuous run process and cooled to a second low temperature below around 100° F., e.g. at cooler 40 (FIG. 2 a).

After it reaches the second low temperature, the section of metallic tubing may be coiled, e.g. about reel 17 (FIG. 2 a).

In a third exemplary method, referring now to FIG. 7, a section of thin walled metallic tubing 12 (FIG. 2 a) having a welded seam and a wall thickness of less than 0.25 inches is extended from a coil mounted about reel 15 (FIG. 2 a) into heater 20 (FIG. 2 a) as part of a continuous run process. The section of metallic tubing 12 is heated to a high temperature in the range of 1300-1600° F. in heater 20 (FIG. 2 a) and then moved from heater 20 to low temperature reservoir 30 (FIG. 2 a) as part of the continuous run process. In low temperature reservoir 30, the section of metallic tubing 12 is quenched to reduce the temperature of the section of metallic tubing 12 to a first low temperature in the range of 500-1000° F. in a time period of less than around 3 seconds.

The section of metallic tubing 12 (FIG. 2 a) is then allowed to transform to bainite. The section of metallic tubing 12 transformed to bainite is then moved out of low temperature reservoir 30 (FIG. 2 a) as part of the continuous run process cooled to a second low temperature below around 100° F., e.g. at cooler 40 (FIG. 2 a).

The foregoing disclosure and description of the inventions are illustrative and explanatory. Various changes in the size, shape, and materials, as well as in the details of the illustrative construction and/or a illustrative method may be made without departing from the spirit of the invention. 

1. A method for austempering thin walled tubing, comprising: a. heating a section of metallic tubing having a wall thickness of less than 0.25 inches to a high temperature in the range of 1300-1600° F. in a heater; b. moving the section of metallic tubing from the heater to a low temperature reservoir as part of a continuous run process; c. quenching the section of metallic tubing in the low temperature reservoir to reduce the temperature of the section of metallic tubing to a first low temperature in the range of 500-1000° F. in a time period of less than 3 seconds; d. allowing the section of metallic tubing to transform to bainite; e. moving the section of metallic tubing transformed into bainite out of the low temperature reservoir as part of the continuous run process; and f. cooling the section of metallic tubing to a second low temperature below 100° F.
 2. The method of claim 1, wherein the heater used for heating is an induction heater.
 3. The method of claim 1, wherein the low temperature reservoir used for quenching is a molten salt bath.
 4. The method of claim 1, wherein the moving is accomplished in part by using rollers.
 5. The method of claim 1, wherein the cooling is accomplished by forced convection.
 6. The method of claim 1, wherein the section of metallic tubing comprises a steel alloy with a carbon content greater than or equal to 0.25 and less than or equal to 0.45.
 7. The method of claim 6, wherein the section of metallic tubing comprises 4130 alloy steel.
 8. The method of claim 1, wherein the section of metallic tubing comprises a time-temperature-transformation curve where the start of conversion to austentite-ferrite is at least 0.75 seconds after quenching in the low temperature reservoir.
 9. The method of claim 1, wherein the heater comprises a flame.
 10. A method for austempering thin walled coiled tubing, comprising: a. extending a section of thin walled metallic tubing having a wall thickness of less than 0.25 inches from a reel mounted coil into a heater as part of a continuous run process; b. heating the section of metallic tubing to a high temperature in the range of 1300-1600° F. in the heater; c. moving the section of metallic tubing from the heater to a low temperature reservoir as part of the continuous run process; d. quenching the section of metallic tubing in the low temperature reservoir to reduce the temperature of the section of metallic tubing to a first low temperature in the range of 500-1000° F. in a time period of less than 3 seconds; e. allowing the section of metallic tubing to transform to bainite; f. moving the section of metallic tubing transformed into bainite out of the low temperature reservoir as part of the continuous run process; and g. cooling the section of metallic tubing to a second low temperature below 100° F.
 11. The method of claim 10, further comprising the step of coiling the section of metallic tubing after it reaches the second low temperature.
 12. The method of claim 10, wherein the low temperature reservoir used for quenching is a molten salt bath.
 13. The method of claim 10, wherein the cooling is accomplished by forced convection.
 14. The method of claim 10, wherein the thin walled metallic tubing wall has a thickness of around 0.120 inches.
 15. An austempered thin walled tubing produced by the method of claim
 10. 16. A method for austempering and stress relieving a thin walled coiled tubing, comprising: a. extending a section of thin walled metallic tubing having a welded seam and a wall thickness of less than 0.25 inches from a reel mounted coil into a heater as part of a continuous run process; b. heating the section of metallic tubing to a high temperature in the range of 1300-1600° F. in the heater; c. moving the section of metallic tubing from the heater to a low temperature reservoir as part of the continuous run process; d. quenching the section of metallic tubing in a low temperature reservoir to reduce the temperature of the section of metallic tubing to a first low temperature in the range of 500-1000° F. in a time period of less than 3 seconds; e. allowing the section of metallic tubing to transform to bainite; f. moving the section of metallic tubing transformed to bainite out of the low temperature reservoir as part of the continuous run process; and g. cooling the section of metallic tubing to a second low temperature below 100° F.
 17. The method of claim 15, wherein the section of metallic tubing comprises a steel alloy with a carbon content greater than or equal to 0.25 and less than or equal to 0.45.
 18. The method of claim 16, wherein the section of metallic tubing comprises 4130 alloy steel.
 19. The method of claim 15, wherein the low temperature reservoir used for quenching is a molten salt bath.
 20. An austempered thin walled and stress relieved welded tubing produced by the method of claim
 15. 21. A thin walled welded tube, comprising: a. an austempered cylindrical body created as part of a continuous run process, the austempered cylindrical body comprising a first seam edge, a second seam edge, and a wall having a thickness of less than 0.25 inches; and b. a stress relieved welded seam joining the first and second seam edges.
 22. The tubing of claim 20, wherein said tubing has a length of at least 200 feet.
 23. The tubing of claim 21, wherein said tubing is coiled on a reel.
 24. The tubing of claim 23, wherein the tubing comprises a first end region attached to at least one of (i) a motor, (ii) an overshoot jar, (iii) an intensifier, (iv) a landing nipple, (v) a plug catcher, (vi) a casing scraper, (vii) a snake pin, (viii) a downhole tool, or (ix) a valve.
 25. The tubing of claim 24, wherein the tubing comprises a second end region opposite the first end region connected to a pump.
 26. An apparatus for austempering thin walled tubing, comprising: a. a heater adapted to accept a section of metallic tubing that has a wall thickness of less than 0.25 inches and heat the section of metallic tubing to a high temperature in the range of 1300-1600° F. in a continuous run process; b. a low temperature reservoir adapted to accept a moving section of the metallic tubing as part of a continuous run process and to reduce the temperature of the section of metallic tubing to a first low temperature in the range of 500-1000° F. in a time period of less than 3 seconds; and c. a cooler adapted to cool the section of metallic tubing to a second low temperature below 100° F.
 27. The apparatus of claim 27, wherein the heater comprises at least one of (i) an induction heater or (ii) a flame
 28. The apparatus of claim 28, wherein the heater is located at least one of (i) proximate the low temperature reservoir or (ii) within the low temperature reservoir. 